• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

battery charging.

Status
Not open for further replies.

manz

New Member
i have a (1) charger with 2 same rated rechargeable batery. the question is,can i charge both of the battery at the same time (the charger is design to charge 1 battery at a time).will it damages the charger/battery? if this can be done,then what is the charging time?woluld it be double?

for the info, the charger output is 7.2V and 250mAH and the battery is 7.2V 650mAH. the normal charging time is 3 hours.

thanks.
 

audioguru

Well-Known Member
Most Helpful Member
Batteries are not exactly the same. If two are in parallel then one would overcharge and the other would undercharge.
 

manz

New Member
alright thanks.so take it as it is not suppost to be done.

audioguru said:
Batteries are not exactly the same. If two are in parallel then one would overcharge and the other would undercharge.
but would the charging time still be the same as charging a single battery?
 

stevez

Active Member
If the current flow is balanced (it probably won't be) then half the power available will go to each battery. The time may not be exactly double because of the behavior of the charger.

Now, some chargers have features that would further confuse things. Is there a temperature sensor? Some charger have one to limit the charge rate. Is there a microprocessor or some other control? Some chargers "know" when a battery is full based on subtle but clear voltage changes.
 

audioguru

Well-Known Member
Most Helpful Member
The charging current will be divided by two batteries in parallel so the time would be longer.
 

poopeater

New Member
audioguru said:
Batteries are not exactly the same. If two are in parallel then one would overcharge and the other would undercharge.
True, but would they be so different that it would actually cause a problem? In all actuality, I'd think that they'd be mismatched to a slight degree, causing one cell to draw slightly more current than the other. Once the 'hungrier' cell got charged, it would then draw around the same as the other cell. Am I missing something?
 

audioguru

Well-Known Member
Most Helpful Member
poopeater said:
In all actuality, I'd think that they'd be mismatched to a slight degree, causing one cell to draw slightly more current than the other. Once the 'hungrier' cell got charged, it would then draw around the same as the other cell. Am I missing something?
Same as two LEDs in parallel. One will have a slightly lower voltage than the other and hog most of the current. Even when it is fully charged it might enter overcharge with its voltage requirement lower than the other one that has barely charged.
 

poopeater

New Member
audioguru said:
Same as two LEDs in parallel. One will have a slightly lower voltage than the other and hog most of the current. Even when it is fully charged it might enter overcharge with its voltage requirement lower than the other one that has barely charged.
There's no way it could hog *all* or even most of the current. It would be a proportionally larger current, but it should even out as the lower voltage cell charged up.
 

Hero999

Banned
Listen to audioguru, connecting batteries of different capacities together is a very bad idea, don't do it!
 

manz

New Member
stevez said:
Is there a temperature sensor? Some charger have one to limit the charge rate. Is there a microprocessor or some other control? Some chargers "know" when a battery is full based on subtle but clear voltage changes.
i dont think so the charger have any of those,coz what i see inside just a simple transformer and a couple of diode and a LED.it is just a very simple and basic charger.

anyway,if there is so much complication by doing so (charge 2 batteries at a time), i think better not to do so and better just go and get another charger for that purpose.

thaks a lot guys.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top